ABC's Jimmy Kimmel, Letterman's fiercest fan in the late-night realm, praised the veteran host on Twitter, writing "David @Letterman is the best there is and ever was.

During Late Night,host Seth Meyers credited Letterman with launching the NBC talk show.

"I grew up on David Letterman," Meyers said. "I remember we used to memorize top ten lists so we could tell them on the bus the next day."

He continued: "There are a lot of things I can't believe about the fact that I get to do this job. The thing I truly can't believe more than all of the others is – Late Night, this was David Letterman's show. If it wasn't for David Letterman, this show wouldn't exist. If I wasn't for David Letterman I wouldn't' be here."

Arsenio Hall called Letterman "a legend," saying he had the pleasure of being both a fan and a competitor.

"He has set a standard for comedy in late night that I strive to achieve every single day," Hall said in a statement. "When I decided to come back to late night and compete against Dave, I received a phone call asking me to be a guest on Dave's CBS show for the first time. Dave put me on his show 72 hours before I debuted. Dave showed that the only thing that matches his comic genius is his class. Late Night might fill his time slot, but it can never fill the void he will leave behind. He is simply the best”

Letterman revealed during a taping of Late Show that he would retire when his CBS contract expires in 2015. The news broke during the afternoon, so it is unclear whether hosts had time to react during the tapings of their own shows. Letterman's CBS colleague Craig Ferguson is in reruns this week, while a rep for Conan O'Brien said the host did not mention it during Thursday's taping of his TBS show.